fix(snap), add the current checked out version as the parent, not the head #9345
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GiladShoham
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Dec 4, 2024
davidfirst
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Dec 18, 2024
In some scenarios, it's needed to maintain some legacy code, for example, the new code is 2.x and the legacy is 1.x which still needs to be maintained. If a patch is needed to 1.x code, the component needs to be checked out to 1.x and tagged with a specific version, for example: `bit tag --ver 1.0.1 --ignore-newest-version`. Currently, when this patch is done, although the history of this patch is correct thanks to a recent [PR](#9345), but the head now points to this patch version. As a result, when importing the component, the user gets 1.0.1 and not 2.x. This PR introduces a new flag `--detach-head` to keep the head intact in this case, so the head still points to 2.x, while the .bitmap is updated to 1.0.1. This new patch 1.0.1 becomes a detached head. It also supports lanes. It's possible to work on multiple components when they're checked out to 1.x, create a new lane, snap some changes, then merge the lane with `--detach-head` flag. This flag, instruct bit to find the common snap before the divergent point, and merge the lane to that point and not to the head. In order for the garbage collector to not delete this detached-head snap, and for the remote to not identify this component as a merge-conflict, we save a new prop `detachedHeads` into `ModelComponent` object. For now, this flag `--detach-head` is under a feature-flag. It'll be enabled by default once bit cloud is deployed with a new version that supports it.
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It's easier to explain this with an example: comp1 has 3 versions: 0.0.1, 0.0.2 and 0.0.3. The head points to 0.0.3. This workspace has comp1 checked out to 0.0.2. The user is now running
bit snap.What should be the parent of this new snap? the checked out version - 0.0.2 or the head - 0.0.3?
Until now, we used the head. In terms of the history, this is incorrect, because it skips the changes done on 0.0.3.
In practice, this is very confusing in the following scenario:
The user now regrets making this snap and to remove it, he/she is running
bit reset. Because this snap was on top of the head, the reset changes the .bitmap version to the head version - 0.0.3 while leaving the files in the filesystem according to 0.0.2. The user continues and runsbit snapagain. Now, the changes done in 0.0.3 are gone. Investigating when these changes are gone, leads to this new snap, which shows it removes the changes. The user made this snap is not aware of all of this.This PR fixes it by using the checked out version as the parent. This leads to a component being diverged, because on the remote went to another direction since this checked out version. Once the user tries to export, it'll throw an error suggesting to either
bit mergeorbit resetand snap again.